/**
 * Generates an authorization signature for API requests.
 *
 * ⚠️ **Warning:** This function should only be run on the server.
 * It uses the API secret, which must remain confidential. Running this
 * code in a client-side environment risks exposing sensitive information
 * to end users or malicious actors.
 *
 * This function creates a signed authorization string using the provided API key and secret.
 * The generated string includes the API key, a timestamp (in seconds since epoch),
 * and a SHA-512 hash signature of the concatenated API key, secret, and timestamp.
 *
 * @param {string} apiKey - The API key used for authentication.
 * @param {string} apiSecret - The API secret used to generate the signature.
 * @returns {string} - A formatted authorization string in the format:
 *                     `APIKey=<apiKey>,signature=<signature>,timestamp=<timestamp>`.
 *
 * @example
 * const apiKey = 'yourApiKey';
 * const apiSecret = 'yourApiSecret';
 * const authSignature = generateAuthorizationSignature(apiKey, apiSecret);
 * console.log(authSignature);
 * // Example output:
 * // APIKey=yourApiKey,signature=2ee76043a90a...,timestamp=1737106896
 */
export declare function generateAuthorizationSignature(apiKey: string, apiSecret: string): string;